From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 9ACACCA101F for ; Fri, 12 Sep 2025 10:42:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=wiKAYHzpCEXoWhfblNLR8Um3ShIc9ndkfPpFFkVadBo=; b=tlQ2gtqGmKLk48GczNFn37K7cM LV1he2M12s4EqE6RImxeG8rD7qd1qM/2wpo+heO1KDRfzvhyJohCu8gj3f+mjXeQyNw5e0ElnDQh2 DmUfuA55Vl53GJNVvtXHarOoNITVFpt8S6BJzdJtSlE7j0BXODjbUkRxnGX/m/rTGvC4M4m+5tbw/ CN635KnCNGBfdjBuejSl2owAreijYb04wWAW5LscjYdk9b62wfdpEJYOgx8S0BeD9DPfRWmY0NIVr I+u80M82irCR0xJrcJsZ6iqtmAUugTDeI76+eM74TWyzBFmpOFOHq44wsr+gE/lprJQIN+uI7TO1b OMnQOW+Q==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1ux1EL-00000008eWG-18TQ; Fri, 12 Sep 2025 10:42:13 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1ux1EJ-00000008eVk-1POM for linux-arm-kernel@lists.infradead.org; Fri, 12 Sep 2025 10:42:12 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 437FA1515; Fri, 12 Sep 2025 03:42:02 -0700 (PDT) Received: from [10.1.196.46] (e134344.arm.com [10.1.196.46]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 505263F66E; Fri, 12 Sep 2025 03:42:05 -0700 (PDT) Message-ID: <13347819-c83d-446b-856e-d7fd8ec742ea@arm.com> Date: Fri, 12 Sep 2025 11:42:03 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 10/29] arm_mpam: Add cpuhp callbacks to probe MSC hardware To: James Morse , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-acpi@vger.kernel.org Cc: D Scott Phillips OS , carl@os.amperecomputing.com, lcherian@marvell.com, bobo.shaobowang@huawei.com, tan.shaopeng@fujitsu.com, baolin.wang@linux.alibaba.com, Jamie Iles , Xin Hao , peternewman@google.com, dfustini@baylibre.com, amitsinght@marvell.com, David Hildenbrand , Dave Martin , Koba Ko , Shanker Donthineni , fenghuay@nvidia.com, baisheng.gao@unisoc.com, Jonathan Cameron , Rob Herring , Rohit Mathew , Rafael Wysocki , Len Brown , Lorenzo Pieralisi , Hanjun Guo , Sudeep Holla , Catalin Marinas , Will Deacon , Greg Kroah-Hartman , Danilo Krummrich , Lecopzer Chen References: <20250910204309.20751-1-james.morse@arm.com> <20250910204309.20751-11-james.morse@arm.com> From: Ben Horgan Content-Language: en-US In-Reply-To: <20250910204309.20751-11-james.morse@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250912_034211_425608_278CB70A X-CRM114-Status: GOOD ( 19.94 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi James, On 9/10/25 21:42, James Morse wrote: > Because an MSC can only by accessed from the CPUs in its cpu-affinity > set we need to be running on one of those CPUs to probe the MSC > hardware. > > Do this work in the cpuhp callback. Probing the hardware will only > happen before MPAM is enabled, walk all the MSCs and probe those we can > reach that haven't already been probed as each CPU's online call is made. > > This adds the low-level MSC register accessors. > > Once all MSCs reported by the firmware have been probed from a CPU in > their respective cpu-affinity set, the probe-time cpuhp callbacks are > replaced. The replacement callbacks will ultimately need to handle > save/restore of the runtime MSC state across power transitions, but for > now there is nothing to do in them: so do nothing. > > The architecture's context switch code will be enabled by a static-key, > this can be set by mpam_enable(), but must be done from process context, > not a cpuhp callback because both take the cpuhp lock. > Whenever a new MSC has been probed, the mpam_enable() work is scheduled > to test if all the MSCs have been probed. If probing fails, mpam_disable() > is scheduled to unregister the cpuhp callbacks and free memory. > > CC: Lecopzer Chen > Signed-off-by: James Morse > --- > Changes since v1: > * Removed register bounds check. If the firmware tables are wrong the > resulting translation fault should be enough to debug this. > * Removed '&' in front of a function pointer. > * Pulled mpam_disable() into this patch. > * Disable mpam when probing fails to avoid extra work on broken platforms. > * Added mpam_disbale_reason as there are now two non-debug reasons for this > to happen. Looks good to me. Reviewed-by: Ben Horgan Thanks, Ben